Stabilization of germanium(ii) by complex formation in iodimetric titration of germanium

Four factors are important in the reduction of germaniuin(IV) by hypophosphite, namely, proper acidity, temperature, proper concentration of complexing ligand, and time of heating. The complexing ligand is needed to stabilize the germaium(II) ions. Halides, with the exception of fluoride, and phosphate are good complexing ligands for germanium. Tin is quantitatively reduced and titrated under the same conditions. Many foreign ions do not interfere, so that prior separation of germanium can often be avoided. Successful results are presented for titrating germanium in the presence of many metals and for direct determination of germanium in actual samples. Germanium after reduction may be titrated with an iodate solution potentiometrically. The formal oxidation potentials of some germanium half-reactions were estimated and used to interpret the stabilization of germanium(II) by complex formation. Phosphoric acid is recommended as the reduction medium.